Obesity is a common disease of unknown etiology. It is a chronic, multifactorial disease that develops from an integration of genetic, environmental, social, behavioral, physiological, metabolic, neuron-endocrine and psychological elements. This disease is considered a cause or co-morbidity to such conditions as GERD, high blood pressure, elevated cholesterol, diabetes, sleep apnea, mobility and orthopedic deterioration, and other consequences, including those limiting social and self image and those affecting the ability to perform certain everyday tasks. Since traditional weight loss techniques, such as diet, drugs, exercise, etc., are frequently ineffective with many of these patients, surgery is often the only viable alternative.
Body Mass Index (BMI) is the most common method used to define the obese patient. This measurement is obtained by taking a person's weight in Kilograms (Kg) and dividing by the square of height in meters. Based on policies set forth by the United States National Institutes of Health (NIH), BMI is used to characterize the degree of excess weight. These categories are listed in Table 1 listed below. Presently, based on current NIH policy, only those people with a BMI of 35 or greater qualify for surgical intervention.
TABLE 1Risk of Associated Disease According to BMI and Waist SizeDisease RiskDisease RiskWaist ≤Waist >Weight40 in. (men) or40 in. (men) orBMIClassification35 in. (women)35 in. (women)18.5 or lessUnderweight—N/A18.5-24.9Normal—N/A25.0-29.9OverweightIncreasedHigh30.0-34.9Obese Class 1HighVery High35.0-39.9Obese Class 2Very HighVery High40.0 to 49.9Morbidly ObeseExtremely HighExtremely High>49.9Super ObeseExtremely HighExtremely High
In the United States, more than 30% of the population is obese as defined in Table 1, including men, women, and children. There are more than 15 million Americans (5.5%) who are morbidly obese. The number of obese children is growing at an alarmingly fast rate. Surgical treatments for obesity continue to be a strong focus of research due to their high level of effectiveness although no treatment is considered ideal. It is well-established in the medical literature that obesity adversely affects general health, and can result in reduced quality of life and reduced lifespan. It is now well-accepted that obesity is associated with increased risk of cardiovascular disease, diabetes and other health issues. In contrast, animal studies show that longevity is increased in lean subjects (Weindruch, R. & Walford, R. L., 1988. The Retardation of Aging and Disease by Dietary Restriction, Thomas, Springfield, Ill.; Spindler, S. R., 2003, in Anti-Aging Therapy for Plastic Surgery, eds. Kinney, B. & Carraway, J., Quality Medical, St. Louis, Mo.). Much work continues to be needed before a widely acceptable solution can be expected.
Surgical weight loss (bariatric) procedures are designed to restrict weight gain by either limiting caloric intake by restricting effective stomach size or by malabsorption, which is reducing the intestine's ability to absorb nutrition. Many surgeons offer their patients a combined procedure that includes a restrictive and malabsorption material. These procedures are irreversible and rely on a surgeon's judgment to estimate the final size of the new restrictive stomach as well as the remaining small intestine length to provide adequate nutrition for optimal weight loss and management for the patient's lifetime.
Presently, bariatric procedures can be performed by open or laparoscopic surgery. Open surgery typically requires a ten day hospitalization and a prolonged recovery period with a commensurate loss of productivity. Laparoscopic procedures have reduced in-hospital stay to three days, followed by a three week at-home recovery. These procedures can even be performed as an outpatient procedure. Laparoscopic procedures have reduced cost considerably, making the minimally invasive laparoscopic procedure available to more patients. In 2000, there were 30,000 bariatric procedures performed, while in 2003, over 90,000 procedures were reported.
One common obesity surgery is the Roux-en-Y gastric bypass (often known only as a “gastric bypass”). During this type of operation, the surgeon permanently changes the shape of the stomach by surgically reducing (cutting or stapling) its size to create an egg-sized gastric pouch or “new stomach.” The rest of the stomach is then divided and separated from this new stomach pouch, greatly reducing the amount of food that can be consumed after surgery. In addition to reducing the actual size of the stomach, a significant portion of the digestive tract is bypassed and the new stomach pouch is reconnected directly to the bypassed segment of small intestine. This operation, therefore, is both a restrictive and malabsorptive procedure, because it limits the amount of food that one can eat and the amount of calories and nutrition that are absorbed or digested by the body. Once completed, gastric bypass surgery is essentially irreversible. Some of the major risks associated with the Roux-en-Y Gastric Bypass procedure include bleeding, infection, pulmonary embolus, anastomotic stricture or leak, anemia, ulcer, hernia, gastric distention, bowel obstruction and death.
Another common obesity surgery is known as vertical banded gastroplasty (“VBG”), or “stomach stapling.” In a gastroplasty procedure, the surgeon staples the upper stomach to create a small, thumb-sized stomach pouch, reducing the quantity of food that the stomach can hold to about 1-2 ounces. The outlet of this pouch is then restricted by a band that significantly slows the emptying of the pouch to the lower part of the stomach. Aside from the creation of a small stomach pouch, there is no other significant change made to the gastrointestinal tract. So while the amount of food the stomach can contain is reduced, the stomach continues to digest nutrients and calories in a normal way. This procedure is purely restrictive; there is no malabsorptive effect. Following this operation, many patients have reported feeling full but not satisfied after eating a small amount of food. As a result, some patients have attempted to get around this effect by eating more or by eating gradually all day long. These practices can result in vomiting, tearing of the staple line, or simply reduced weight loss. Major risks associated with VBG include: unsatisfactory weight loss or weight regain, vomiting, band erosion, band slippage, breakdown of staple line, anastomotic leak, and intestinal obstruction.
A third procedure, the Duodenal Switch, is less common. It is a modification of the biliopancreatic diversion or “Scopinaro procedure.” While this procedure is considered by many to be the most powerful weight loss operation currently available, it is also accompanied by significant long-term nutritional deficiencies in some patients. Many surgeons have stopped performing this procedure due to the serious associated nutritional risks.
In the Duodenal Switch procedure, the surgeon removes about 80% of the stomach, leaving a very small new stomach pouch. The beginning portion of the small intestine is then removed, and the severed end portions of the small intestine are connected to one another near the and of the small intestine and the beginning of the large intestine or colon. Through this procedure a large portion of the intestinal tract is bypassed so that the digestive enzymes (bile and pancreatic juices) are diverted away from the food stream until very late in the passage through the intestine. The effect of this procedure is that only a small portion of the total calories that are consumed are actually digested or absorbed. This irreversible procedure, therefore, is both restrictive (the capacity of the stomach is greatly reduced) and malabsorptive (the digestive tract is shortened, severely limiting absorption of calories and nutrition). Because of the very significant malabsorptive material of this operation, patients must strictly adhere to dietary instructions including taking daily vitamin supplements, consuming sufficient protein and limiting fat intake. Some patients also experience frequent large bowel movements, which have a strong odor. The major risks associated with the Duodenal Switch are: bleeding, infection, pulmonary embolus, loss of too much weight, vitamin deficiency, protein malnutrition, anastomotic leak or stricture, bowel obstruction, hernia, nausea/vomiting, heartburn, food intolerances, kidney stone or gallstone formation, severe diarrhea and death.
One relatively new and less invasive form of bariatric surgery is Adjustable Gastric Banding. Through this procedure the surgeon places a band around an upper part of the stomach to divide the stomach into two parts, including a small pouch in the upper part of the stomach. The small upper stomach pouch can only hold a small amount of food. The remainder of the stomach lies below the band. The two parts are connected by means of a small opening called a stoma. Risks associated with Gastric Banding are significantly less than other forms of bariatric surgery, since this surgery does not involve opening of the gastric cavity. There is no cutting, stapling or bypassing.
It has been found that the volume of the small upper stomach pouch above the band increases in size up to ten times after operation. Therefore the pouch volume during surgery needs to be very small, approximately 7 ml. To enable the patient to feed the stomach with sufficient nutrition immediately after an operation considering such a small gastric pouch, the stoma initially needs to be relatively large and later needs to be substantially reduced, as the pouch volume increases. To be able to achieve a significant range of adjustment of the band, the cavity in the band has to be relatively large and is defined by a thin flexible wall, normally made of silicone material. Furthermore, the size of the stoma opening has to be gradually reduced during the first year after surgery as the gastric pouch increases in size. Reduction of the stoma opening is commonly achieved by adding liquid to the cavity of the band via an injection port to expand the band radially inwardly.
A great disadvantage of repeatedly injecting liquid via the injection port is the increased risk of the patient getting an infection in the body area surrounding the injection port. If such an infection occurs, the injection port has to be surgically removed from the patient. Moreover, such an infection might be spread along the tube interconnecting the injection port and the band to the stomach, causing even more serious complications. Thus, the stomach might be infected where it is in contact with the band, which might result in the band migrating (eroding) through the wall of the stomach. Also, it is uncomfortable for the patient when the necessary, often many, post-operation adjustments of the stoma opening are carried out using a relatively large injection needle penetrating the skin of the patient into the injection port.
It may happen that the patient swallows pieces of food too large to pass through the restricted stoma opening. If that occurs the patient has to visit a doctor who can remove the food pieces, if the band design so permits, by withdrawing some liquid from the band to enlarge the stoma opening to allow the food pieces to pass the stoma. The doctor then has to add liquid to the band in order to regain the restricted stoma opening. Again, these measures require the use of an injection needle penetrating the skin of the patient, which is painful and uncomfortable for the patient, and can sometimes be the cause of infection, thus risking the long-term viability of the implant. The adjustment of the band can be inconsistent. For example, if some air is inadvertently injected with the liquid (sterile saline), it can cause some compressibility to the pressurization media and take away some of the “one-to-one” feel when pressurizing and depressurizing.
The LAP-BAND Adjustable Gastric Banding System (Inamed) is a product used in the Adjustable Gastric Banding procedure. The LAP-BAND system, includes a silicone band, which is essentially an annular-shaped balloon. The surgeon places the silicone band around the upper part of the stomach. The LAP-BAND system further includes a port that is placed under the skin, and tubing that provides fluid communication between the port and the band. A physician can inflate the band by injecting a fluid (such as saline) into the band through the port. As the band inflates, the size of the stoma shrinks, thus further limiting the rate at which food can pass from the upper stomach pouch to the lower part of the stomach. The physician can also deflate the band, and thereby increase the size of the stoma, by withdrawing the fluid from the band through the port. The physician inflates and deflates the band by piercing the port, through the skin, with a long, non-coring needle. There is often ambiguous feedback to the physician between the amount injected and the restriction the patient feels during the adjustment procedure, such as when swallowing a bolus of liquid to test the stoma. In addition, a change of as little as 0.5 ml or less can sometimes make a difference between too much restriction and the correct amount of restriction.
The lower esophageal sphincter (LES) is a ring of increased thickness in the circular, smooth muscle layer of the esophagus. At rest, the lower esophageal sphincter maintains a high-pressure zone between 15 and 30 millimeters (mm) Hg above intragastric pressures. The lower esophageal sphincter relaxes before the esophagus contracts, and allows food to pass through to the stomach. After food passes into the stomach, the sphincter constricts to prevent the contents from regurgitating into the esophagus. The resting tone of the LES is maintained by myogenic (muscular) and neurogenic (nerve) mechanisms. The release of acetylcholine by nerves maintains or increases lower esophageal sphincter tone. It is also affected by different reflex mechanisms, physiological alterations, and ingested substances. The release of nitric oxide by nerves relaxes the lower esophageal sphincter in response to swallowing, although transient lower esophageal sphincter relaxations may also manifest independently of swallowing. This relaxation is often associated with transient gastroesophageal reflux in normal people.
Gastroesophageal reflux disease, commonly known as GERD, results from incompetence of the lower esophageal sphincter, located just above the stomach in the lower part of the esophagus. Acidic stomach fluids may flow retrograde across the incompetent lower esophageal sphincter into the esophagus. The esophagus, unlike the stomach, is not capable of handling highly acidic contents so the condition results in the symptoms of heartburn, chest pain, cough, difficulty swallowing, or regurgitation. These episodes can ultimately lead to injury of the esophagus, oral cavity, the trachea, and other pulmonary structures.
Evidence indicates that up to 36% of otherwise healthy Americans suffer from heartburn at least once a month, and that 7% experience heartburn as often as once a day. It has been estimated that approximately 1-2% of the adult population suffers from GERD, based on objective measures such as endoscopic or histological examinations. The incidence of GERD increases markedly after the age of 40, and it is not uncommon for patients experiencing symptoms to wait years before seeking medical treatment, even though mild cases can be successfully treated with lifestyle modifications and pharmaceutical therapy. For patients, who are resistant, or refractory, to pharmaceutical therapy or lifestyle changes, surgical repair of the lower esophageal sphincter is an option.
The most common surgical repair, called fundoplication surgery, generally involves manipulating the diaphragm, wrapping the upper portion of the stomach, the fundus, around the lower esophageal sphincter, thus tightening the sphincter, and reducing the circumference of the sphincter so as to eliminate the incompetence. The hiatus, or opening in the diaphragm is reduced in size and secured with 2 to 3 sutures to prevent the fundoplication from migrating into the chest cavity. The repair can be attempted through open surgery, laparoscopic surgery, or an endoscopic, or endoluminal, approach by way of the throat and the esophagus. The open surgical repair procedure, most commonly a Nissen fundoplication, is effective but entails a substantial insult to the abdominal tissues, a risk of anesthesia-related iatrogenic injury, a 7 to 10 day hospital stay, and a 6 to 12 week recovery time, at home. The open surgical procedure is performed through a large incision in the middle of the abdomen, extending from just below the ribs to the umbilicus (belly button).
Endoscopic techniques for the treatment of GERD have been developed. Laparoscopic repair of GERD has the promise of a high success rate, currently 90% or greater, and a relatively short recovery period due to minimal tissue trauma. Laparoscopic Nissen fundoplication procedures have reduced the hospital stay to an average of 3 days with a 3-week recovery period at home.
Another type of laparoscopic procedure involves the application of radio-frequency waves to the lower part of the esophagus just above the sphincter. The waves cause damage to the tissue beneath the esophageal lining and a scar (fibrosis) forms. The scar shrinks and pulls on the surrounding tissue, thereby tightening the sphincter and the area above it. These radio-frequency waves can also be used to create a controlled neurogenic defect, which may negate inappropriate relaxation of the LES.
A third type of endoscopic treatment involves the injection of material or devices into the esophageal wall in the area of the lower esophageal sphincter. This increases the pressure in the lower esophageal sphincter and prevents reflux.
One laparoscopic technique that appears to show promise for GERD therapy involves approaching the esophageal sphincter from the outside, using laparoscopic surgical techniques, and performing a circumference reducing tightening of the sphincter by placement of an adjustable band such that it surrounds the sphincter. However, this procedure still requires surgery, which is more invasive than if an endogastric transluminal procedure were performed through the lumen of the esophagus or stomach, such as via the mouth. Furthermore, the necessity to provide for future adjustment in the band also requires some surgical access and this adjustment would be more easily made via a transluminal approach.
For both treatment of obesity and GERD, gastric banding has proven to be a desirable treatment option. However, despite the advantages provided by gastric banding methods, they nonetheless suffer from drawbacks that limit the realization of the full potential of this therapeutic approach. For example, slippage may occur if a gastric band is adjusted too tight, or too loose, depending on the situation and the type of slippage. Slippage can also occur in response to vomiting, as occurs when a patient eats more food that can be comfortably accommodated in the upper pouch. During slippage, the size of the upper pouch may grow, causing the patient to be able to consume a larger amount of food before feeling full, thus lowering the effectiveness of the gastric band. On the other hand, erosion may occur if the gastric band is adjusted or secured too tightly. In either case detecting slippage or reducing the risk of erosion may be accomplished by adjusting the device to provide a proper flow rate.
Furthermore, current methods of adjusting gastric bands and restriction devices require invasive procedures. For example, one method requires penetration of the abdomen with a needle in order to withdraw or inject a solution from a subcutaneous access port that is connected to a tube that in turn regulates the inflation of the gastric band. Infection and patient discomfort and pain are related to the use of the needle required to fill the gastric band with saline. As a result, non-invasively adjustable gastric bands have been proposed, some of which seek to provide a correct reading of the inner diameter of the gastric band at all times. However, because the wall thickness of the stomach is not uniform from patient to patient, the actual inner diameter of the stomach at the stoma opening will be unknown. Thus the size of the opening of the band is at best an approximation of the stomal opening that connects the smaller upper pouch and the remainder of the stomach.
As a result, in order to properly adjust a gastric band some method of measuring flow through the device or otherwise related the luminal aperture of the alimentary canal at the side of the band is needed. Current methods typically make use of radiological procedures such as X-ray fluoroscopy of barium sulfate suspensions. However, the use of X-ray procedures in a significant number of patients is highly undesirable. The majority of gastric banding patients undergoing therapy to treat obesity are women of child-bearing age. The first few weeks of pregnancy, when a mother may be unaware she is pregnant, is an especially critical time of fetal development, and exposure to X-rays is to be avoided if at all possible. In addition, while fluoroscopy can monitor flow of a radio-opaque material such as barium sulfate, it is not particularly well suited to provide accurate information about the size of the band aperture, the size of the lumen in the alimentary canal where the band is placed, or whether the band is causing secondary problems such as erosion of the gastric wall. Thus it would be desirable to have a gastric banding system that included a non-invasive means of adjusting and monitoring band function in the patient that improves on the prior art methods.